The use of microemulsions for the separation of laminates is known, for example, from the Applicant's co-pending patent application No. WO 2012/101189, which teaches the separation of layers in a multiple layer material from each other. The examples of this disclosure are directed towards the separation of multiple layer materials used in photovoltaic modules.
The requirement to improve the recycling of laminates used in food packaging has been discussed. For example, an article on “The recycling of tetra pak aseptic cartons” by Mario Abreu (found on www.environmental-expert.com) discusses this issue extensively and notes that the recycling of cellulose tissues is possible, but the separation of polyethylene from the aluminum foil is not possible.
U.S. Pat. No 5,421,526 (Tetra Laval) teaches a method of recovering individual material components, such as metal, plastic and, where applicable, paper, from waste of laminated packaging materials comprising layers of metal, plastic and possibly paper or cardboard. The layers are separated from each other by treating the waste with an organic acid or a mixture of organic acids, selected from among formic acid, acetic acid, propanoic acid, butyric acid and other similar volatile organic acids. The method of this patent is carried out at a high temperature (80° C.), close to the flash point of acetic acid (ca. 90° C. at 80% concentration), which not only requires a large amount of energy, but also adds a safety risk. The mixture used is because of the high concentration (80%) of acetic acid highly aggressive. This mixture will attack the aluminum components and lead to formation of hydrogen, as well as a loss of the amount of aluminum recovered in the process.
European Patent Application EP 0 543 302 A1 (Kersting) teaches a method for separating aluminum foil from plastic foils, such as PE foils, to enable the recycling of the aluminum. The laminates are placed in a 20% solution of low fatty acids (e.g. acetic acid, propionic acid, formic acid, butonoic acid) and heated to 100° C. for 10-20 minutes. The method is preferably carried out in a closed vessel to operate the liquid at and/or above its boiling point. In addition, an underpressure can be created as the solution is cooled.